Homology (chemistry)
In chemistry, homology is the appearance of homologues. A homologue is a compound belonging to a series of compounds differing from each other by a repeating unit, such as a methylene bridge −−, a peptide residue, etc.
A homolog is a special case of an analog. Examples are alkanes and compounds with alkyl side chains of different length.On the periodic table, homologous elements share many electrochemical properties and appear in the same group of the table. For example, all noble gases are colorless, monatomic gases with very low reactivity. These similarities are due to similar structure in their outer shells of valence electrons. Mendeleev used the prefix eka- for an unknown element below a known one in the same group.
